OIL 'RIG' DISPOSAL
Comparing the environmental impacts of
disposing of Brent Spar on land and at sea.
■
The 'best practicable environmental option'.
■
Implications of recent events.
The controversy over the proposed disposal in
deep water of the Brent Spar storage buoy reveals
disagreement over the environmental impact of
sea disposal and how this is taken into account in
deciding the Best Practicable Environmental Option for disposing of redundant N Sea installations.
■
This note examines environmental impacts from
disposing of oil platforms etc., and the issues raised1.
ASSESSING ENVIRONMENTAL IMPACTS
Dismantling and Disposal on Land
Before an installation can be dismantled on land it
needs to be brought ashore. Any ballast water or other
sources of contamination must be removed and treated
before disposal. Adequate safeguards are required to
prevent pollution of coastal or estuarine waters.
Environmental benefits arise from onshore disposal
chiefly in the raw material and energy savings from
recycling scrap metals. Different environmental, health
and safety issues arise for different aspects of the
operation. Key aspects include:
●
Dismantling larger structures presents physical
dangers to workers, and health risks can arise from
removing asbestos (e.g. in fire-proofing). Other
safeguards are necessary against inhaling dust from
scale which may contain radioactive elements naturally present in the oil reservoir2.
●
Waste materials require careful and controlled handling. Concrete and other non-recyclable materials
(e.g. wood, plastic and glass) can be disposed of in
a licensed landfill site. Oily residues and sludges
may need to be incinerated. The LSA scale in
pipework and elsewhere may classify scrap or
sludges as low-level radioactive waste and require
transport to Dounreay or Drigg for disposal.
●
Cutting up large structures uses large amounts of
energy and generates noise, fumes and dust.
Disposal at Sea
Scientific research in the 1960s first turned the spotlight
on the possible environmental consequences of dumping wastes at sea, and underpinned pressure for international regulation, which emerged in 1972 via the Oslo
Convention (North Sea and North-east Atlantic), and
London Dumping Convention (covering the whole
world). The Conventions were enacted in the UK via
the Dumping at Sea Act 1974 (now the 1985 Food and
Environmental Protection Act -FEPA) and fisheries
departments are responsible for evaluating the envi-
POST
note
65
July
1995
POSTnotes are intended to give Members an overview
of issues arising from science and technology. Members
can obtain further details from the PARLIAMENTARY
OFFICE OF SCIENCE AND TECHNOLOGY (extension 2840).
ronmental impacts of proposals to dump waste materials and for the necessary licensing schemes3. Predicting
the possible impacts of waste on the marine environment broadly consists of evaluating the characteristics
of the waste (physical, chemical, biochemical and biological properties; toxicity; persistence and potential
for bio-accumulation in marine organisms); effects on
living resources, public health and amenity; and issues
raised by the proposed method or site of disposal.
When the Oslo convention was first introduced there
were substantial quantities of waste dumped by several coastal states in all three categories of industrial
waste, sewage sludges and dredged spoils. However,
increasingly, scientific assessments of the acceptability
of dumping at sea have been overlain by the 'precautionary principle' and a philosophy that wastes should
be disposed of on land wherever possible. This trend
has been strengthened by agreements at the North Sea
Conferences and has led to industrial waste dumping
being phased out altogether this year, and agreement
reached to phase out sewage sludge by 1998. After that
date the only waste disposed of routinely at sea will be
dredgings (from ports etc.).
This was the backdrop against which more specific
rules and guidance were developed for oil and gas
platform decommissioning and disposal. Rules developed under the Oslo and Paris Conventions apply to
the North Sea, and specify that all actions shall be
licensed and decided on a case-by-case basis; also that:●
No permit shall be issued if the installation contains
substances which result or are likely to result in
hazards to human health, harm to living resources
and marine ecosystems, damage to amenities or
interference with other legitimate uses of the sea.
●
Other contracting parties should be consulted.
Additional global guidelines focusing primarily on the
navigational safety aspects come from the International Maritime Organisation (IMO) and include:●
In water depths of less than 75 metres (100 metres
after 1998), all installations weighing less than 4,000
1. This note is complementary to Library Briefing 95/77, which examines
inter alia, the international regulatory environment for disposal.
2. Low specific activity (LSA) scale forms on the insides of ballast or
storage tanks in a similar manner to limescale in plumbing. However in
this case, the salts involved contain low levels of naturally-occurring
radioactive elements.
3. Ministry of Agriculture, Fisheries and Food - MAFF (England and
Wales); Scottish Office Agriculture and Fisheries Dept (SOAFD).
P. O. S. T.
●
Note
65
tons should be entirely removed.
For deeper/ heavier installations, partial removal is
permitted; where left wholly or partly in place, the
potential effects on the marine environment evaluated should include effects on water quality; the
potential for pollution or contamination of the site
by residual products from, or deterioration of, the
installation; and interference with other uses of the
sea such as fishing, shipping, cable laying etc.
THE BPEO FOR DISPOSAL
Environmental protection policy in the UK applies the
principle of Best Practicable Environmental Option
(BPEO) which seeks to eliminate or minimise releases
of harmful substances to the environment as a whole,
while taking account of safety, practical feasibility and
costs. Options for decommissioning and disposing of
oil and gas installations include:
●
complete removal to land disposal and recycling;
●
complete removal to shallow or deep-sea disposal;
●
partial removal - leaving only the lowest parts of the
supports (‘the stump’) in place - the rest to land or
shallow or deep-sea disposal;
●
emplacement or toppling - severing the top section,
which is placed (or allowed to fall) alongside the
stump, leaving at least 55m clearance to the surface.
Deciding the BPEO is a complex procedure. The activities involved are set out in detail for each of the options
under consideration. A comparative assessment is
then made for the environmental impacts on air, water
and land, the technical steps and risks involved, the
health and safety implications, the financial costs and
any other relevant factors.
Where the BPEO involves disposal at sea, the main
approvals would follow the pattern illustrated in Figure 1, involving MAFF/SOAFD and DTI as the primary regulators, each having to issue a licence - DTI for
the overall "abandonment programme"; MAFF or
SOAFD for any dumping involved. Many other agencies and organisations would be involved in consultation or on specific aspects (e.g. disposal of LSA).
THE SPECIFIC CASE OF BRENT SPAR
Brent Spar was a floating storage buoy, commissioned
in 1976, comprising an above-water helideck and accommodation and equipment decks, over a submerged
oil storage cylinder with buoyancy tanks and ballast
(Figure 2). Its six storage tanks could hold up to 50,000
tonnes (tes) of oil and the overall height is 137m. In
terms of original construction materials, it comprised
nearly 7,000 tes of concrete and haematite (iron ore)
ballast, and 7,500 tes of steel, giving a total weight of
14,500 tes. Since taken out of operation in 1991, the
superstructure has been stripped down, movable items
taken off, and the storage tank drained of oil and refilled
July 1995
FIGURE 1 PROCEDURE FOR DISPOSAL PLAN APPROVAL
OIL COMPANY
Safety case to Health
and Safety Executive
Decommissioning and
Disposal Plan
Department of Trade
and Industry
DTI Approval under
Petroleum Act (1987)
Environmental experts
BPEO Analysis, Environmental Impact Hypothesis
(if sea disposal BPEO)
Dumping at sea Licensing
Authority (MAFF or SOAFD)
Dumping at Sea Licence
with sea water. The current contents of the tank are thus
a residual oily sludge which could not be pumped out,
the sea water and additives (glyoxal for removing
hydrogen sulphide), and contaminants which have
dissolved into the sea water (e.g. oil from the sludge,
zinc from sacrificial anodes used to control corrosion of
the tank). Some key components of the detailed inventory on which Departments based their assessment of
environmental impact and BPEO are listed in Table 2.
The burden of demonstrating the BPEO to the regulatory authorities falls to the facility operator and Shell
commissioned over 30 separate studies to consider the
technical, safety and environmental implications of
disposal, including 3 independent evaluations of the
BPEO. These concluded that the environmental effects
of deep-sea and land-based disposal were each negligible. Deep-sea disposal was the preferred option because it presented fewer safety risks, and was technically simpler and thus much cheaper. In addition, the
environmental consequences of an accidental release or
sinking during the operations needed would be greater
in coastal waters than in the deep ocean (see Box 1).
The DTI approved the abandonment programme on 20
December 1994, and the BPEO evaluation and Impact
Hypothesis were sent to the Oslo and Paris Commissions on 16 February 1995 to notify contracting parties
of the UK Government’s approval of Shell’s proposals.
Final licences were issued in May and the Brent Spar
was towed towards a disposal site in the north Atlantic,
selected by SOAFD on the basis of a separate site
assessment exercise to minimise environmental impact
and avoid interference with other legitimate uses of the
sea. Greenpeace launched a campaign centred on
claims that the environmental impacts would be greater
than stated, and opposition to deep-sea disposal followed from the Governments of Germany, Denmark
Netherlands and Sweden. In the light of this opposition, a consumer boycott, and violence in Germany,
Shell announced on the day before the buoy reached its
final destination (June 20), that the company would
seek to dispose of the structure on land, even though
the company (and the UK Government) still believed
deep-sea disposal to be the BPEO.
P. O. S. T.
FIGURE 2
Note
65
July 1995
Box 1 THE BRENT SPAR BPEO ASSESSMENTS
SCHEMATIC DIAGRAM OF BRENT SPAR
Helideck
Accommodation and
equipment decks
Outer buoyancy tanks
Inner buoyancy tanks
137
metres
Main storage
Central shaft
Fixed ballast
Table 2
Material
MATERIALS REMAINING AT BRENT SPAR
Weight in tonnes Material
Steel + other metals
Sand/Scale
Aluminium
Copper
PCBs
7570
90
29
14
0.0002
Weight in tonnes
Haematite/Concrete
Hydrocarbons
Zinc
Other heavy metals
Total
6800
51
14
less than 1
14568
Greenpeace based its initial claims that a considerable
threat existed to the marine environment on the same
information as the licensing authorities. The latters'
scientific assessment had however concluded that there
would be a negligible environmental impact because:●
The oily sludge4 contained primarily the heavy
(tarry) components of oil which are relatively inert;
●
Contaminated seawater4 leaking from the tank into
the surrounding waters would be diluted, and direct toxic effects, if any, would be limited to within
the immediate vicinity of the leak. The quantities of
metals etc. in the water were insufficient to affect the
quality of marine life in the area (which is in any case
very sparse and not part of the human food chain).
●
The main impact was essentially seen as physical,
i.e. the equivalent to a wreck of a similar size, which
would disturb the marine sediment and its organisms, but would weather and ultimately provide a
new surface for fixed animals to grow on.
Greenpeace also expressed concern there had been no
recent structural survey, and questioned whether the
Spar would reach the seabed intact if dumped. SOAFD
however point out that maintaining containment was
not an important factor in the impact assessment.
When Greenpeace personnel boarded the rig, samples
were taken which suggested the presence of thick
layers of oil, rather than lightly contaminated seawater,
and Greenpeace thus argued that the BPEO case had
been based on inadequate information and the dumping licence should be reassessed. Shell has stated that
the main tanks are inaccessible from above and believes
that Greenpeace sampled vent pipes which had not
been cleaned; the total amount of oil in these would be
small and still within the amount declared on its origi4. These were referred to by Greenpeace as "toxic sludge" and "lethal
chemical cocktails" respectively.
The BPEO assessments used in support of the decision to dump
by the UK Government reviewed in detail the two leading candidates of horizontal dismantling and on-shore disposal, and deep
water disposal. These two options compared as follows:Environmental Considerations. Horizontal dismantling should
have negligible impacts on the marine environment, but if the
structure failed during the stressful rotation of the buoy into the
horizontal position, any contaminated ballast water released
would enter the more sensitive coastal environment; equally, if the
structure sank this would create a hazard to navigation and
fishing. For deep water disposal, the environmental effects would
also be negligible as the impacts were expected to be largely
physical, i.e. burial of organisms; any local toxic effects on marine
life due to contamination would be very localised and because of
the low densities of organisms in the deep ocean, effects insignificant. The site was selected to avoid any danger of interaction with
other uses of the deep ocean, e.g. fishing, submarine cables and
military activities.
Safety and Risk Implications. Horizontal dismantling is much
more labour-intensive, and involves complex and potentially
hazardous operations. The risk analysis suggests that the
probabilities of fatal injuries are some six times greater than those
of deep water disposal. On-shore dismantling also involves
potential exposure to the LSA scales, asbestos etc. and therefore
requires strict health and safety controls throughout.
Engineering complexity and cost. The much greater engineering complexity of rotating the rig and dismantling it is reflected in
the different initial cost estimates - £12 million for deep water
disposal and £46 million for horizontal dismantling.
The BPEO thus concluded that the environmental impacts of each
option were evenly balanced, but the health and safety considerations and engineering complexity and cost considerations strongly
favoured the deep sea disposal option.
nal application. These discrepancies were being investigated by the licensing authorities until the decision
was taken by Shell to cancel the dump, but the authorities had the necessary power to delay disposal while
the discrepancies were resolved.
GENERAL ISSUES
The UK has placed consistent emphasis on developing
flexible and pragmatic approaches to waste disposal
under the broad philosophy that evaluating cases on
their merits ensures the most benefit from the inevitably finite amounts spent on environmental protection.
The Brent Spar experience however raises questions
over how far such ‘rational’ approaches can prevail
where the final decision involves the sea with its
common use by many countries, and differing interpretations (e.g. of the precautionary approach) under international controls and regulations. There are a number
of strands to this question.
Firstly, as already mentioned, the BPEO involves comparing impacts on different (land, sea, air) environments, and balancing local air pollution against, say,
disturbance to deep-sea sediments is inevitably somewhat subjective. More quantitative means of assessing
P. O. S. T.
Note
65
environmental impact are being tried under FEPA, and
by Her Majesty’s Inspectorate of Pollution (HMIP),
whereby numerical scores are assigned for the severity
of the environmental effects; these can be combined
with scores for costs and other risks to give an Integrated Environmental Index (IEI). The approach with
the lowest IEI would be the BPEO.
In theory, such approaches should ensure that the
BPEO selected offers tangible benefits over other options without jeopardising the financial viability of the
operation. However, it is exactly this blend of environmental protection with economic pragmatism that
proves so difficult to ‘sell’ to campaign organisations
and some other Governments, and the Brent Spar
experience shows that existing means of disseminating
the analyses and explaining decisions have not persuaded the public to resist calls to mount consumer
boycotts, etc. The question follows therefore whether
refining current methodology will change this.
As described above, the Brent Spar case has also fallen
foul of disputes over the exact nature and quantity of
contaminants on the structure. As licensing authority,
SOAFD specified the information it required to make a
proper assessment of environmental impact, and this
was provided by Shell and independent analysts. The
recently-disputed quantity estimates would have little
effect on the impact hypothesis, but it is possible that
more comprehensive data could have helped public
understanding of the case. In this context, the licensing
authority has powers to require samples to be taken,
and these could have been used to measure the exact
degree of contamination (rather than infer it), and also
determine its toxicity to marine life via toxicity tests.
But underlying the whole debate are fundamental differences in the way in which the role of the sea is
perceived in different countries. UK policy has been to
see the sea as part of the overall environment to be
protected and managed, but ever since the start of the
Oslo Convention, it has been clear that some other
countries consistently see the sea as a medium to be
specially protected - if necessary to the point that its use
for certain types of waste disposal should be barred
altogether (e.g. for dumping of radioactive waste) or
used only as an option of last resort. Thus, while the
UK’s approach to the decommissioning and disposal of
oil and gas installations is consistent with international
standards which allow for the possibility of deep-sea
disposal where this is the BPEO, recent events show
how far the scientific basis of BPEO is being challenged
by a philosophical opposition to sea disposal and calls
for a reassessment of the whole decision-making process. If, for whatever reason (commercial or political),
Shell’s decision to abandon deep-sea disposal sets a
trend, what repercussions will this have on the abandonment of future installations in the UK sector?
July 1995
There are currently 219 installations in the UK sector of
the North Sea (about half of all structures present).
Three-quarters of these are relatively straightforward
to decommission and were already going to be disposed of on land, but it was intended that about 50
deep-water installations would be assessed in a similar
way to the Brent Spar, and the full range of disposal
options (described earlier) evaluated.
The 50 deep-water installations include 7-8 with functions similar to the Brent Spar, such as offshore loading
units, which would be difficult to bring ashore for
disposal, and the Energy Minister has suggested that
deep-sea disposal could represent the BPEO for them.
In the light of Shell's abandonment of plans for deepsea disposal of the Brent Spar, some groups argue that
all such installations should be disposed of on land, and
that the protracted and expensive (preparing Shell's
BPEO case cost £2.5M) evaluations of BPEO could be
reduced. The UK Offshore Operators Association
(UKOOA) report that only 1-2 of these more difficult
installations will have to be decommissioned within
the next 10 years, so that if alternative facilities for
onshore dismantling do not currently exist in the UK,
there is time to evaluate the pros and cons of adapting
existing platform construction or other sites to allow
the UK to compete for contracts in this field, and for
carrying out more of the initial dismantling at sea.
The outcome of the Brent Spar debate has however
caused many to be concerned that 'holistic' decisions
taken as a result of looking at the overall strength of a
case to dispose of at sea or on land are reversed by
focusing on only one aspect. In particular, some have
pointed to the lack of priority assigned to human health
and safety considerations in the debate, and argue that
they should carry at least as much weight in decisionmaking as environmental protection - indeed, the Offshore Installations (Safety Case) Regulations (1992)
stipulate that operators must demonstrate how the
risks involved in decommissioning will be reduced to
as low as reasonably practicable (Figure 1).
Regardless of the fate of the limited number of 'special'
structures, there would be even greater implications of
a more comprehensive land-only policy which ruled
out abandonment of the 'stumps' or other partial removal mechanisms for all 50 or so deep-water installations. The industry points out that the costs of
decommissioning over the next 10 years under current
policies are already estimated at £1,500M, and increases
on this will reduce or remove the economic viability of
the more marginal North Sea fields. A 'clear seas'
philosophy applied to all installations including in situ
abandonment of pipeline systems could cost £3,000M
extra (spread over many years), two thirds of which are
borne by the tax-payer under current arrangements.
Copyright POST, 1995.